Stroboscopic lamp circuits

ABSTRACT

A voltage boosting means is provided in a stroboscopic lamp firing circuit for substantially increasing the available voltage for firing the lamp at the point in time that the normal striking means is operated to ready the lamp for firing. The substantial increase in voltage for firing the lamp is provided by a capacitor which is charged to or partly to the normal firing voltage prior to initiation of the striking means for the lamp. A switch means utilized to initiate the striking means is able to sense the points in time at which the boosted voltage appears at the lamp, and will initiate the striking means at the proper time to utilize this boosted voltage. Since the operation of the switch means, which operation also operates the striking means, occurs when the boosted voltage is available to the lamp, substantially increased voltage is provided at the proper time for assuring firing of the lamp.

United States Patent Henry N. Swimen [72] Inventor Los Angeles, Calif.[21] Appl. No. 874,098 [22] Filed Nov. 5, 1969 [45] Patented Aug. 24,1971 [54] STROBOSCOPIC LAMP CIRCUITS 6 Chhns, 6 Drawing Figs.

[52] US. Cl. 315/200, 315/208, 3151241 [51] Int. Cl. 1105b 37/00 [50]FleldotSeai-cli 315/200, 208, 219, 241, 241 P, 227, 262; 320/1 [56]References Cited UNIT ED STATES PATENTS 2,953,721 9/1960 Chauvineau315/241 3,229,158 1/1966 Jensen 315/241 X 3,354,351 11/1967 Ward 315/241X Primary Examiner-Roy Lake Assistant Examinerl.awrence J. DahlABSTRACT: A voltage boosting means is provided in a stroboscopic lampfiring circuit for substantially increasing the available voltage forfiring the lamp at the point in time that the nonnal striking means isoperated to ready the lamp for firing. The substantial increase involtage for firing the lamp is provided by a capacitor which is chargedto or partly to the normal firing voltage prior to initiation of thestriking means for the lamp. A switch means utilized to initiate thestriking means is able to sense the points in time at which the boostedvoltage appears at the lamp, and will initiate the striking means at theproper time to utilize this boosted voltage. Since the operation of theswitch means, which operation also operates the striking means, occurswhen the boosted voltage is available to the lamp, substantiallyincreased voltage is provided at the proper time for assuring firing ofthe lamp.

PATENTEUAUGZMQH 3600.996

SHEET 1 OF 2 2 VI PEAK INVENTOR 3 HENRY N. SWITSEN BY &

ATTOR/VE Y5 STROBOSCOPIC LAMP CIRCUITS This invention relates toimproved stroboscopic lamp firing circuits for greatly increasing thereliability of operation of the BACKGROUND OF THE INVENTION stroboscopiclighting is well known in the art and has a wide range of uses.Essentially, a stroboscope incorporates a gas discharge lamp capable ofemitting an extremely intense flash of light for an extremely short timeduration. The firing circuit for the lamp is generally designed suchthat the lamp can be successively fired at various repetition rates orfrequencies or, fired only once at a desired instant in time. In fairlysophisticated stroboscopic lamp circuits, extremely accurate repetitionrates can be achieved and the lamp itself is thus useful in timingoperations; for example, in monitoring moving machine parts. In simplerversions, a stroboscopic lamp is very useful in photography for takingflash pictures wherein the lamp need only be flashed once at a giveninstant in time. In still other versions, a relatively simple circuitcan be provided for flashing the lamp at a relatively low frequency suchas from 1 to 30 times per second and wherein the particular frequency ofthe flashing is not of primary importance. This type of lamp is usefulfor psychedelic lighting effects.

The present invention is primarily concerned with the foregoing types ofstroboscopic lamps wherein fairly simplified and economical firingcircuits may be provided. However, it is to be understood that theinvention is applicable to all types of stroboscopic lamps. 1

Essentially, the firing circuit for such lamps includes a voltage sourcewhich may constitute an AC source, or battery powered AC sourceconnected to charge a storage capacitor through a resistance. The lampis connected across the capacitor and when not operated presents a veryhigh resistance so that the source voltage can readily be stored on thecapacitor. The circuit is completed by a striking means which generallytakes the form of a high step-up transformer capable of applying atrigger pulse which serves to strike a small arc within the lamp; thatis, effect at least a partial ionization of the gas in the lamp. If thevoltage across the storage capacitor and thus across the lamp issufficient to fire the lamp, the gas suddenly becomes highly ionized andthe resistance of the lamp becomes very low. As a result, a very highcurrent is drawn through the lamp from the storage capacitor and thedesired high intensity flash from the lamp results. Discharge of thepower on the storage capacitor through the lamp reduces the voltage fromthe source across the lamp to a low value so that the lamp extinguishesitself. At this point, the lamp again presents a very high resistanceand the storage capacitor can then become recharged through theresistance and the circuit is ready for a subsequent firing. The maximumrepetition rate of firing is thus determined in part by the timeconstant of charging of the storage capacitor since it is essential thatthe storage capacitor be sufficiently charged before a subsequent firingto provide the necessary voltage to fire the lamp.

One of the major problems in the foregoing types of circuits is theassuring that a sufficient voltage from the voltage source exists acrossthe lamp at the time of striking of the lamp. In the case of portablestroboscopic lighting units wherein batteries are often used for thevoltage source, the available voltage for firing the lamp generallydecreases over prolonged use simply as a result of degradation of thebatteries. Thus reliability of firing of the lamp is impaired. Inaddition, physical changes take place in the lamp itself such thatincreased voltages are necessary to fire the same over those necessarywhen the lamp is first used. Many other factors may also determinewhether or not a sufficient voltage is available to fire the lamp.

In order to increase reliability of stroboscopes, the first step hasbeen to assure that a sufficient voltage is available to fire the lampat the time of striking of the lamp. Assurance of a sufficient voltagehas sometimes been accomplished in the past by utilizing a step-uptransformer between the voltage source and the lamp itself. However,this involves additional circuit elements and oftentimes will requiremore expensive type storage capacitors. Even under these circumstances,the storage capacitor itself can be damaged from too much voltage. Itwould be highly desirable to provide some means for assuring thatsufficient voltage is available with present-day circuits employed inthe more simplified versions of stroboscopic lighting all to the endthat economy can be realized in the manufacture of such stroboscopicsystems and yet the desired increased reliability of operation can beassured.

BRIEF DESCRIPTION OF THE PRESENT INVENTION With the foregoingconsiderations in mind, it is a primary object of the present inventionto provide an improved stroboscopic lamp firing circuit wherein avoltage of higher value than that normally appearing on the storagecapacitor is applied to the lamp at the time of striking of the lampwherein this higher voltage is derived from the normal voltage sourcealready available in the lamp circuit, all to the end that a greatlyincreased reliability of operation is assured.

Briefly, the foregoing is accomplished by incorporating elements in thelamp circuit in the form of booster means for raising the voltage fromthe source means for firing the lamp. The result is that a substantiallyincreased voltage is provided across the lamp at the point in time ofstriking of the lamp to thereby efiect complete ionization andsufficiently lower the resistance of the lamp that power from thestorage capacitor can be assured of passing through the lamp. In thepreferred embodiment of the invention, the booster means takes the formof a single additional capacitor to the circuit and a cooperating diode.The arrangement is such that the capacitor is charged from the voltagesource through the diode to a given voltage. One side of the capacitoris connected to the lamp, and the other side is connected to the sourcein such a manner that a boosted voltage appears on the first siderelative to ground when the initiating means is operated to strike thelamp. The diode prevents back flow of current from the boost capacitorthrough the storage capacitor or the firing circuit so that the boostedvoltage is applied across the lamp at the point in time of striking ofthe lamp. The result is an assurance of complete ionization of the gasin the lamp so that the energy stored in the storage capacitor canreadily discharge through the lamp.

The advantages of the foregoing arrangement are numerous. First, byutilizing the booster means, a higher voltage type of lamp can be usedwith. a lower voltage circuit. Further, if the condition of the lamp issuch that an increased voltage across it is necessary to fire the same,the lamp can still be fired reliably even though the voltage across thestorage' capacitor is not sufficient to fire the lamp. Thus the usefullife of the lamp can be substantially increased.

Moreover, for a given time constant of recharge of the storagecapacitor, a faster flash repetition rate can be achieved since it isnot essential that the storage capacitor be completely charged at thetime of firing in view of the presence of the boosted voltage.Alternatively, for a given flash repetition rate, a longer time constantof recharge for the capacitor can be used.

Since it is possible to use a lower source voltage, the breakdownvoltage rating of the storage capacitor can be lower for a given lamp.Step-up transformers heretofore thought necessary can also beeliminated. In addition, apparatus for sensing the phase of the incomingAC source may have additional advantages, such as striking the lamp on anegative peak and eliminating lamp current in the positive side of therectifier system.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of theinvention will be had by now referring to the accompanying drawings, inwhich:

FIG. 1 represents a typical simplified prior art type of stroboscopiclamp and firing circuit therefor;

FIG. 2 illustrates the same circuit as FIG. 1 except for theincorporation of the voltage boosting means of the present invention andthe use of an SCR as one possible switch means;

FIG. 3 is a qualitative plot of voltage values during a firing of thelamp appearing at one of the lamp terminals useful in explaining theoperation of the invention;

FIG. 4 is a modified circuit in accordance with the invention, utilizingnegative boost;

FIG. 5 is a further modification of the circuit of FIG. 1; and

FIG. 6 shows still another modification of the circuit of FIG.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, there isillustrateda simplified stroboscopic lighting circuit including an ACsource 10, connected across a storage capacitor C by way of leads l1 and12. A gas discharge lamp 13 which may be of the xenon type also connectsacross the leads 11 and 12 so that voltage stored on the capacitor Cappears across the lamp 13.

A striking circuit enclosed within the dashed outline 14 includes atransformer 15. The primary of the transformer coil 15 connects throughtap 16 and condenser Ct to a lead 17 arranged to be energized from thevoltage source and storage .capacitor C through a switch means S whenclosed to a junction point 18 in the lead 11. A high dischargeresistance R! connects between the junction point of the lead 17 and condenser Ct and the lead 12. The secondary of the transformer 15terminates in a coil 20 surrounding the lamp 13. The resistance R,capacitor 21, and diodes 22 and 23 comprise a charging circuit for thestorage capacitor C.

The foregoing elements are entirely conventional. The switch means S,while shown as a simple mechanical-type switch, may constituteelectrical contacts to be closed as in the case of a photographic strobelamp circuit or may constitute any type of electronic switch such as avacuum tube, solidstate element, or other equivalent means for closingthe circuit between the junction points 18 and 19.

In the operation of the circuit of FIG. I, assume that the switch meansS is open as shown. Under these conditions, the voltage VI of the ACsource will result in a current flow through the resistance R to chargethe capacitors C through the charging circuit elements 21, 22, and 23which define a one-half wave doubler. The resistance of the lamp l3 whenit is not fired, is extremely high so that the peak voltage storedacross the capacitor C will correspond substantially to 2V1. This samevoltage will also appear across the lamp 113 by way ofthe leads 11 and12.

The switch 5 essentially constitutes an initiating means for thestriking circuit 14. When the switch S is closed, the voltage 2Vl (peak)will be applied to the junction point 19 and capacitor Ct. Since thevoltage across a capacitor cannot change instantaneously, the same 2V1(peak) volts will energize the primary of the transformer through thetap 16 in the form of a transient or high rate of change voltage as thecapacitor Ct charges. This changing voltage in the primary will bereflected in an extremely large voltage generated in the secondary ofthe coil 15 in accord with the step-up ratio of the turns. The highsecondary voltage will be applied to the coil and result in the strikingof a small arc in the gas in the lamp 13; that is, at least a partialionization of the gas will occur. At this point, the voltage across thestorage capacitor C appears across the lamp 13, and if sufficientlyhigh, will cause an avalanching of the ionization and a discharging ofthe stored energy through the lamp.

The discharge through the lamp 13 results in a highly intense flash oflight. Since the resistance of the lamp 13 is dropped to an extremelylow value, the discharge from the storage capacitor C is extremelyrapid, and the voltage across the lamp drops to a relatively low valueso that the lamp is extinguished.

When the lamp has completed its firing, it will assume its former veryhigh resistance value so that the storage capacitor C will then commencerecharging through the resistance R and elements 21, 22, and 23. If theswitch S should remain closed, the small striking circuit capacitor Ctwill also be charged to the voltage value 2V1 (peak) and the lamp cannotbe refired until the switch is opened so that the striking circuitcapacitor C! can discharge through Rt. After the striking circuitcapacitor Ct has completed its discharge, reclosing of the switch S willresult in a subsequent firing of the lamp l3.

The condition of firing of the lamp 13 in the above described operationis that the voltage 2V1 (peak) from the voltage source across the lampbe of a sufficient value to fire the lamp when the striking circuitoperates. This sufficient voltage," as mentioned heretofore, depends onthe lamp involved. If the voltage source in the form of a batterypowered AC source provides a voltage just sufficient to fire the lamp,it is very possible after prolonged use that the voltage will degrade asa consequence of aging of the battery to a value in which the lamp willnot fire. Altemately, and as also described heretofore, repeated use ofthe lamp can result in the necessity of a higher firing voltage with ageof the lamp. Thus, in the circuit of FIG. 1 unless some type of veryhigh initial voltage source is provided, the reliability of firing ofthe lamp is subject to the foregoing conditions.

Referring now to a first embodiment of the present invention as shown inFIG. 2, assurance of a sufficient voltage across the lamp at the pointin time of striking of the lamp is realized by providing an increasedpeak voltage from the voltage source at the lamp terminal in the lead 11and initiating striking of the lamp at the proper point in time that thepeak voltage is present. Towards this end, the switch S of FIG. 1, isreplaced by an SCR 24 in FIG. 2 with its gate lead 25 connecting throughvariable resistance Rt and lead 26 to the source 10 as at 27. A voltagebooster means takes the form of a lead 28 including a small capacitor 29connected between the lamp terminal at the point 30 and the AC source ata junction point 31 (other points in the AC source could also be used).

Cooperating with this small capacitor is a diode 32 connected betweenthe point 30 of connection of the capacitor to the lamp terminal and thejunction 18 of the SCR switch means with the storage capacitor C.

With the foregoing additional elements in the circuit, substantiallyhigher than the normally available voltage across the lamp is providedto the lamp if the striking means is energized at the proper phase or"the AC source voltage. This phase is sensed by the gate lead 25 of theSCR.

The foregoing is depicted in FIG. 3, wherein the waveform 33 of thevoltage at the lamp junction 30 during a firing operation is shown.Thus, when the SCR 24 is closed by voltage from the AC source at thetime depicted by the vertical line Tl, voltage waveform portion 34reaches a peak at the lamp terminal 30 as indicated at 35. This voltageis more than sufficient to assure firing of the lamp 13 so thatdischarge from the storage capacitor will take place through the lamp tothe point in time designated by the vertical line T2. At this point, thevoltage across the lamp is sufficiently low that the lamp isextinguished. The portion of the curve 36 represents the charging of thestorage capacitor C. The time interval between Tl and T2 is greatlyexaggerated in FIG. 3 for purposes of clarity. Actually, this timeinterval represents the duration of the flash of the lamp and inpractice could be of the order of milliseconds or microseconds.

FIG. 4 illustrates a slightly modified circuit from that shown in FIG.2. In this respect, some of the same numerals have been employed todesignate corresponding components as in FIG. 2. The circuit of FIG. 4essentially applies the boosted voltage to the negative side of the lampterminal rather than the positive side. Towards this end, and referringspecifically to FIG. 4, the SCR switch is illustrated at 37 havingatrigger gate terminal 38 connected through the variable resistance R!to a junction 39 between a voltage divider comprising resistances R1 R2.R2.A diode 40 (corresponding to the diode 23 in FIG. 2) cooperates withthe diode 22, resistance R, and capacitor 21' to define the half-wavedoubler charging circuit for the storage capacitor C. However, the diode32 of FIG. 2 constituting part of the boost voltage circuit is replacedby a diode 41 in FIG. 4 and the capacitor 29 of FIG. 2 connected into aline 42 connecting from the lower lamp terminal 43 of the lamp 13 andterminating at the junction 27 of the AC source as indicated at 44. Thevariable resistance Rt connecting to the junction point 39 of theresistance voltage divider defined by R1 and R2 senses the negativephase of the voltage source rather than the positive phase as describedin conjunction with FIG. 2. The SCR 37 in turn is arranged to initiatethe striking means during negative phase peaks of the voltage from thesource 10. With this arrangement, the boosted voltage is boosted in anegative sense so that the voltage across the lamp at the time ofstriking is again substantially increased.

FIG. 5 illustrates a standard voltage quadrupler for providing a boostvoltage except that the added capacitors may be very small compared tothe storage capacitor. These capacitors in the quadrupler circuit can bemade small since, in the configuration shown, they need not contributesignificant illumination to the power of the lamp.

Thus with specific reference to FIG. 5, it will be noted that thecircuit is substantially the same as the prior art circuit of FIG. 1except for the quadrupler components. The additional elements areincluded in a line 45 in the form of capacitor 46,

diode 47, diode 48, and capacitor 49.

FIG. 6 is similar to FIG. 5 except that the two additional diodes andtwo additional capacitors are connected to the negative lamp terminaland serve to supply negative boosted voltage. Thus, in FIG. 6, a line 50connects to the negative lamp terminal 51 and includes diodes 52 and 53along with capacitor 54, the other side of the line 50 terminating atthe AC source at 55. The final capacitor is shown at 56 connected in theline 12 to the negative lamp terminal 51. In the circuit of FIG. 6, apositive half-wave doubler cooperates with a negative half-wave doublerto provide in effect a quadrupled boosted voltage across the lamp.

OPERATION With the foregoing brief description of the circuits in mind,their operation will now be fully described. Starting first with theoperation of the circuit of FIG. 2, and with reference to FIG. 3, assumefirst that the SCR switch means 24 is open (that is, nonconducting).Under these conditions, the storage capacitor C will be charged up tothe 2V1 peak voltage J through the charging resistance R and theone-half wave doubler elements 21', 22, and 23. This one-half wavedoubler is shown merely as a typical circuit. It should be understoodthat a full-wave rectifier, full-wave doubler, tripler or evenquadrupler, could be used. The capacitor 29 can be substantially smallerthan the storage capacitor C but the same 2V1 peak voltage will appearacross the capacitor 29. The voltage at the lamp terminal 30, however,will now have an AC voltage equal to V1 riding on a DC level equal to2V1 peak. There is thus applied to the lamp a voltage which variesbetween 2V1 peak and 4V1 peak depending upon the phase of V1 at anygiven point in time.

The foregoing quiescent situation is depicted by the initial portion 34of the curve of FIG. 3 between 0 and the time T1. If the SCR 24 istriggered or closed at the time T1, 4V1 peak voltage will be availableat the lamp to start heavy ionization of the gas. The value 4V1 peak isnow greater than the value of voltage on the storage capacitor by anamount equal to 2V1 peak. Thus, a boosted voltage has been realized. Thecapacitor 29 could be connected to other points on the AC source, suchas point 27 rather than point 31.

The lamp terminal 30 will thus exhibit a peak voltage as in-Simultaneously, with the closing of the SCR switch, the

stored voltage is applied across the striking circuit capacitor Ctresulting in the transient current in the primary of the transformer 15providing an extremely high voltage on the secondary to strike the lamp.It should be noted that the lower lead of the transformer 15 could beconnected to the line 11 rather than the line 12 in FIG. 2; that is, atthe junction point 18. This connection would reverse the action of Ct;that is, whether it charges or discharges during firing. The importantfeature of the invention is the fact that the boosted voltage appears atthe point 30 at the same point in time as the striking of the lamp 13 asa result of the striking circuit being responsive to the proper phase ofV l.

The manner in which the foregoing proper phase response is accomplishedis as follows. After a discharge has taken place through the lamp 13,capacitors C and Ct are charged up as indicated by the portion 36 of theplot in FIG. 3. The point 19 of Ct is thus somewhere near the value of2V] peak. As the VI source voltage cycles down from its peak, thepotential at the point,27 falls towards a value of -V1 peak. This changein voltage causes point 27 to be negative with respect to the gateterminal 25 of the SCR 24 and the junction point 19. At this point, itshould be understood that for the particular one-half wave doublercircuit shown, the point 27 will never be more positive than a value ofVI peak.

Since the junction point 18 can be at a value of 2V1 peak, the junction19 will assume this 2V1 peak value when the SCR switch 24 closes. Thus,after firing, the junction point 19 will be above the value VI peak.

As the voltage at the junction point 27 falls towards its negative peakvalue, it causes a current flow through the resistor Rt from thejunction 19. This flow makes the SCR gate terminal 25 negative withrespect to its cathode and the reversed biased gate breaks down topermit discharge of capacitor Ct. (If it should be desired that thereverse bias gate to cathode junction not be used for this particularfunction, an external diode can be added across the gate and cathodeleads or a blocking diode could be added in series with the gate andanother resistor connected to the cathode lead and tied to ground oranother suitable point.) p

The discharging of capacitor Ct through the resistance R! continuesuntil the AC voltage at the point 27 rises above the voltage at thejunction 19 by an amount sufficient to fire the SCR. Such can occur onlyafter one cycle or after a number of cycles as determined by the timeconstant of the resistor R! and capacitor Ct. By making Rt variable, itcan thus be used as a flash rate control.

From the foregoing, it will be evident that the positive gate drive tofire the SCR can only occur at a peak or near a peak of the V1 voltagesince at any value less than a peak or near a peak, the condenser Ct isstill discharging through Rt and thus through the reversed biased gate.

Several possible alternate connections could be used to accomplish theforegoing phase sensing. However, with the particular connectionsdescribed and shown in FIG. 2, a minimum number of component partsaccomplishes the desired end.

In the event it should be desired to shift the firing point with respectto the incoming AC phase signal, a voltage divider could be used acrossthe AC source and the resistance R! could be connected at a midpositionon this divider. Since the source is AC, the divider could be reactiveor resistive.

Referring once again to FIG. 3, with the high peak value of voltage asindicatedat 35 appearing across the lamp 13 at the point in time ofstriking of the lamp, firing of the lamp is assured and the discharge ofthe high voltage will take place as shown between the lines TI and T2.When the voltage at the lamp terminal 30 decreases sufficiently belowthe stored voltage on the capacitor C so that the diode 32 can nowconduct, the power or energy stored on the storage capacitor C will allavalanche through the lamp 13 to provide the desired high intensityflash. In this respect, it should be noted that the diode 32 is in asense functioning as a switch since it permits the boosted voltage to beretained at the lamp terminal 30 at the time of its generation; that is,the capacitor 29 cannot discharge back through the diode 32 and storagecapacitor because of the orientation of the diode 32. Thus, it isassured that the increased voltage is available across the lamp at thetime of striking. Since the capacitor 29 does not appreciably contributeto lamp illumination, it can be made very small compared to the storagecapacitor C.

After the lamp 13 is extinguished; that is, at the time T2 as shown inFIG. 3, and when the SCR switch is open (that is, off), the storagecapacitor C will then again be charged as indicated by the curve 36through the resistance R and halfwave doubler circuit preparatory to asubsequent firing of the lamp. Also, the capacitor 29 will be chargedthrough the diode 32 preparatory to providing the increased voltage allas described when a subsequent firing is to take place.

The circuit of FIG. 4 operates in substantially the same manner as thecircuit of F IG. 2 except that the boosted voltage is negative andapplied to the lower lamp terminal 43. Also, the SCR switch 37 is causedto be actuated on a negative peak of the source voltage, the gateterminal 38 being returned through the resistance Rt to a voltagedivider across the AC source comprising the resistances RI and R2. Thegate for the SCR is connected at the junction 39 of these resistances.The phase sensing is similar to that described for FIG. 2 except thatthe SCR is energized on negative peaks since the cathode now has an ACpotential which can fall faster than the gate potential. This isaccomplished by returning the transformer 15 and the SCR anode to thejunction of diode 22 and capacitor 21 as shown in FIG. 4 so they willhave full AC source voltage applied to them while the SCR gate 38 isreturned to point 39 which has less than full AC source voltage appliedto it.

With the SCR switch nonconducting, the capacitor 44 will thus charge upto a given voltage peak through the diode 41. When the SCR switch isclosed to initiate action of the striking circuit during a negative peakof the source voltage, the negative 2V1 peak voltage will be availableat the terminal 43 of the lamp since the negative V1 charge on thecapacitor 44 will be added to the negative VI peak from the source 10.The total boosted voltage across the lamp taking into account the +2Vlpeak voltage at the upper terminal will thus be 4V1 peak voltage.

As in the case of the circuit of FIG. 2, many alternate connections arepossible in the circuit of FIG. 4 including the additional diodes andreactive components to effect a change in the Rt'-Ct time constantrange, phase shift of the switch closure, and striking energy level.Also, as transformer 15 and capacitor Ct are effectively in series, theycan be reversed in termination so that transformer 15 connects to theSCR cathode and capacitor Ct connects to the SCR anode.

The operation of the circuit of FIG. is precisely the same as thatdescribed for the prior art circuit of FIG. 1 except for the provisionof a quadrupled peak voltage for the lamp 13. The doubling of the 2V]peak voltage is accomplished by the additional diodes 47 and 48 andadditional capacitors 46 and 49, the lamp terminal for the lamp 13 nowconnecting to the junction of the diode 48 and capacitor 49. Contrary toconventional prior art circuits however, the additional capacitors 46and 49 can be extremely small compared to the storage capacitor C sincethey do not contribute significant illumination to the lamp. Thissmaller capacity value is at least onetenth and preferably less than oneone-hundredth the capacity of storage capacitor C. The same is true ofthe boost capacitors 29 and 44 of FIGS. 2 and 4 respectively. Thesecapacitors, although small, provide a significantly increased voltage tothe lamp so as to insure initial firing of the lamp. The added diodesact as switches to pass the stored capacitor charge to the lamp afterthe lamp begins to fire.

The operation of FIG. 6 is similar in effect to FIG. 5 except that thetwo additional diodes and two additional capacitances 52, 53 and 54, 56are connected to the negative lamp terminal 51 and supply a negativeboost voltage of 2V1. In essence, FIG. 6 thus provides a positiveone-half wave doubler in cooperation with a negative one-half wavedoubler to provide the total of 4V1 peak across the lamp. The

In the circuits of FIGS. 2, 4, 5, and 6, the term voltage source is usedherein to designate generally the combination of the AC source 10,charging resistance R, and onehalf wave doubler. The term initiatingmenas is used to designate the switch S or the SCRs as described as oneform of such switch since the closing of the switch initiates operationof the striking circuit. The term striking means is meant to cover thevarious elements enclosed within the dashed line 14 of FIG. 1 and thecorresponding elements in FIG. 2.

From the foregoing, it will be appreciated that the present inventionhas provided very simple and economical circuits for vastly improvingthe reliability of stroboscopic lighting circuits.

What I claim is:

1. In a stroboscopic lamp firing circuit including an AC voltage sourceand striking means, the combination comprising: initiating means foroperating said striking means, said initiating means comprising a switchmeans connected between said voltage source and said striking means;booster means for raising the voltage from said source means for firingsaid lamp, said booster means including a capacitor connected betweensaid lamp and said AC source; and a diode connected between the point ofconnection of said capacitor to said lamp and the junction of saidswitch means and said source, said diode permitting charging of saidcapacitor by said voltage source when said switch means is open andblocking current flow from said capacitor through said switch means whensaid switch means is closed, said initiating means being responsive tothe phase of said AC source to operate said striking means at the samepoint in time that boosted voltage is available at said lamp.

2. A circuit according to claim 1, in which said boosted voltage is apositive voltage and said initiating means is responsive to positivepeak, or close to peak values of said AC source.

3. A circuit according to claim I, in which said boosted voltage is anegative voltage and said initiating means is responsive to negativepeak, or close to peak values of said AC source.

4. A circuit for assuring firing of a stroboscopic gas discharge lampcomprising, in combination:

a. a storage capacitor;

b. a source means connected to said storage capacitor providing a givenAC voltage for charging said storage capacitor for firing said lamp;

c. striking means coupled to said lamp for effecting at least a partialionization of gas in said lamp to ready said lamp for firing;

d. means for initiating operation of said striking means including aswitch means connected between said source means and said strikingmeans, said switch means having a connection to said source means andresponsive to a peak voltage of said source means to close; and

e. voltage boosting means connected between said lamp and source forproviding a varying voltage to said lamp, said voltage boosting meansincluding a capacitor connected between said lamp and said source means;and a diode connected between the point of connection of said capacitorto said lamp and said storage capacitor, said means initiating operationof said striking means at a point in time corresponding to a given phaseof said AC voltage when said varying voltage is at or near a peak valueto thereby provide a substantially increased voltage to said lamp oversaid given voltage at the time of striking of said lamp, whereby firingof said lamp is assured.

5. A circuit according to claim 5, in which said AC source includes ahalf-wave doubler circuit, the voltage across said lamp at the time offiring being substantially four times the peak value of AC voltage insaid source passed to said halfwave doubler circuit.

6. A circuit for assuring firing of a stroboscopic gas discharge lampcomprising, in combination:

a. a storage capacitor; e. voltage boosting means connected between saidlamp and b. a source means connected to said storage capacitor sourcefor providing a boosted voltage to said lamp, said idi a given AC voltaefo h i id storage voltage boosting means including at least onecapacitor a acitor for fi ing aid l connected between said lamp and saidsource and at least c. striking means coupled to said lamp for effectingat least a one cofmected betwFen Sa1d lamP and sifld Storage partialionization of gas in said lamp to ready said lamp capacitor, said onecapacitor having a capacitance less for firing. than one-tenth thecapacity of said storage capacitor.

d. means for initiating operation of said striking means; and

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 00,996Date August 24, 1971 lnvent fl Henry N. Switsen It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

In the drawing, Fig. 4, the direction of the diode, Element 41 should bereversed.

Signed and sealed this 17th day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents ORM 204050 USCOMM-DC wan-Pen ,5. GOVRNMENT PI'NTNG OFFICE f1... 0."33.

1. In a stroboscopic lamp firing circuit including an AC voltage sourceand striking means, the combination comprising: initiating means foroperating said striking means, said initiating means comprising a switchmeans connected between said voltage source and said striking means;booster means for raising the voltage from said source means for firingsaid lamp, said booster means including a capacitor connected betweensaid lamp and said AC source; and a diode connected between the point ofconnection of said capacitor to said lamp and the junction of saidswitch means and said source, said diode permitting charging of saidcapacitor by said voltage source when said switch means is open andblocking current flow from said capacitor through said switch means whensaid switch means is closed, said initiating means being responsive tothe phase of said AC source to operate said striking means at the samepoint in time that boosted voltage is available at said lamp.
 2. Acircuit according to claim 1, in which said boosted voltage is apositive voltage and said initiating means is responsive to positivepeak, or close to peak values of said AC source.
 3. A circuit accordingto claim 1, in which said boosted voltage is a negative voltage and saidinitiating means is responsive to negative peak, or close to peak valuesof said AC source.
 4. A circuit for assuring firing of a stroboscopicgas discharge lamp comprising, in combination: a. a storage capacitor;b. a source means connected to said storage capacitor providing a givenAC voltage for charging said storage capacitor for firing said lamp; c.striking means coupled to said lamp for effecting at least a partialionization of gas in said lamp to ready said lamp for firing; d. meansfor initiating operation of said striking means including a switch meansconnected between said source means and said striking means, said switchmeans having a connection to said source means and responsive to a peakvoltage of said source means to close; and e. voltage boosting meansconnected between said lamp and source for providing a varying voltageto said lamp, said voltage boosting means including a capacitorconnected between said lamp and said source means; and a diode connectedbetween the point of connection of said capacitor to said lamp and saidstorage capacitor, said means initiating operation of said strikingmeans at a point in time corresponding to a given phase of said ACvoltage when said varying voltage is at or near a peak value to therebyprovide a substantially increased voltage to said lamp over said givenvoltage at the time of striking of said lamp, whereby firing of saidlamp is assured.
 5. A circuit according to claim 5, in which said ACsource includes a half-wave doubler circuit, the voltage across saidlamp at the time of firing being substantially four times the peak valueof AC voltage in said source passed to said half-wave doubler circuit.6. A circuit for assuring firing of a stroboscopic gas discharge lampcomprising, in combination: a. a storage capacitor; b. a source meansconnected to said storage capacitor providing a given AC voltage forcharging said storage capacitor for firing said lAmp; c. striking meanscoupled to said lamp for effecting at least a partial ionization of gasin said lamp to ready said lamp for firing; d. means for initiatingoperation of said striking means; and e. voltage boosting meansconnected between said lamp and source for providing a boosted voltageto said lamp, said voltage boosting means including at least onecapacitor connected between said lamp and said source and at least onediode connected between said lamp and said storage capacitor, said onecapacitor having a capacitance less than one-tenth the capacity of saidstorage capacitor.